Preparation of sludge-based flocculation-nutrition multifunctional agent and application of sludge-based flocculation-nutrition multifunctional agent in recycling of muck slurry

Abstract

The invention discloses a sludge-based flocculation-nutrition multifunctional agent, a preparation method and application of the sludge-based flocculation-nutrition multifunctional agent in muck mud recycling, and belongs to the technical field of solid waste recycling. The invention relates to a preparation method of a sludge-based flocculation-nutrition multifunctional agent. The preparation method comprises the following steps: carrying out hydrothermal carbonization reaction on sludge under the condition of adding NaOH to obtain and separate hydrothermal carbon and nitrogen-rich water phase residues; leaching the hydrothermal carbon in HCl to obtain and separate acid-soaked hydrothermal carbon and a phosphorus-rich leaching solution; mixing the nitrogen-rich water phase residues and the phosphorus-rich leaching liquor, and standing to obtain humic acid precipitate; after sufficient precipitation, NaOH and MgCl2 are added into the mixture, and struvite precipitation is obtained; and putting the acid-soaked hot charcoal, the humic acid precipitate and the struvite precipitate into a polydiene dimethyl ammonium chloride solution, stirring, and separating to obtain the humic acid / struvite composite material. The multifunctional agent can be used for realizing deep resource utilization of the sludge and fully recovering organic matters, nitrogen, phosphorus and the like contained in the sludge.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource utilization, and specifically relates to a sludge-based flocculation-nutrition multifunctional agent, a preparation method and application thereof in the resource utilization of slag slurry. Background Art

[0002] In recent years, the annual production of municipal sewage sludge and construction waste slurry (generated from tunnel construction, foundation pit excavation, and other processes) has remained high. Traditional landfill disposal not only consumes significant land resources, but also poses a serious threat to the ecological environment through issues such as heavy metal migration and pathogenic bacteria spread caused by leachate. Currently, sludge resource utilization struggles to fully utilize the organic matter and nutrients contained in sludge, resulting in generally low value for resource-based products. Dewatering of construction waste sludge, a typical bulk municipal solid waste, is a key step, but it generally relies on synthetic flocculants such as polyacrylamide. While this can reduce the moisture content of construction waste sludge to around 80%, residual monomers can easily cause soil compaction. Furthermore, the organic matter content of treated construction waste is less than 1.5%, and the total nitrogen and phosphorus content is less than 0.8%, making it difficult to directly utilize. This technological disconnect has led to a vicious cycle of low recovery efficiency, incomplete resource utilization, and secondary pollution in the treatment of sewage sludge and construction waste sludge. An innovative system combining targeted component conversion and multi-effect coupling is urgently needed.

[0003] Existing technologies such as "A MnOx-modified biochar, its preparation method, and application" (Publication No. CN118807733A), "A method for preparing a composite adsorption material using bentonite modified from printing and dyeing sludge" (Publication No. CN117899807A), and "A method for recovering phosphorus from sludge" (Publication No. CN119285185A) only partially utilize sludge components and recover some of the sludge's nutrients. Therefore, existing sludge resource recovery technologies do not fully utilize sludge, resulting in low product value.

[0004] The prior art "A method for improving the yield of hydrothermal humic acid and its application" (Publication No.: CN118388792A) requires the additional addition of alkaline additives for pH adjustment; in the struvite crystallization step, the nitrogen-rich aqueous phase residue obtained in the previous step is used as a nitrogen source process, which effectively reduces the addition of additional nitrogen sources; the prior art "A process for preparing high-efficiency adsorbents for collaborative phosphorus recovery using sludge / iron tailings" (Publication No.: CN118831562A) requires the additional addition of nitrogen sources when recovering sludge phosphorus, but the reagent costs of these prior arts are relatively high.

[0005] The prior art "A water-rich shield slag dehydration composite improver and dehydration method" (publication number: CN118006337A) provides a method for preparing a shield slag dehydration composite improver and a dehydration method, but it can only achieve slag dehydration. The dehydrated slag still needs to be combined with other processes for further disposal or utilization; the prior art "A method for regenerating planting soil from dredged silt" provides a method for preparing planting soil based on dredged silt, but it cannot solve the problem of synchronous dehydration of high-water-content slag slurry.

[0006] Therefore, a sludge-based flocculation-nutrition multifunctional agent, a preparation method and its application in the resource utilization of sludge are proposed. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a sludge-based flocculation-nutrition multifunctional agent, a preparation method and its application in the resource utilization of slag slurry, thereby solving the problems in the prior art.

[0008] The purpose of the present invention can be achieved through the following technical solutions:

[0009] A method for preparing a sludge-based flocculation-nutrition multifunctional agent comprises the following steps:

[0010] The sludge is subjected to hydrothermal carbonization reaction under the condition of adding NaOH to obtain and separate hydrothermal char and nitrogen-rich aqueous phase residue;

[0011] leach the hydrothermal charcoal in HCl to obtain and separate the acid-leached hydrothermal charcoal and the phosphorus-rich leachate;

[0012] The nitrogen-rich aqueous phase residue and the phosphorus-rich extract are mixed and allowed to stand to obtain a humic acid precipitate; after the precipitation is sufficient, NaOH and MgCl2 are added thereto to obtain a struvite precipitate;

[0013] The acid-soaked hydrothermal charcoal, humic acid precipitate and struvite precipitate are placed in a polydiallyl dimethyl ammonium chloride solution, stirred and then separated to obtain the product.

[0014] Furthermore, during the hydrothermal carbonization reaction, the amount of NaOH added is 2% to 10% of the sludge mass.

[0015] Furthermore, the hydrothermal carbonization reaction temperature is 180°C to 220°C.

[0016] Furthermore, the solid-liquid ratio during the hydrothermal carbonization reaction is 1:10.

[0017] Furthermore, the HCl concentration is 0.1M to 1.0M.

[0018] Furthermore, the solid-liquid ratio of the hydrothermal carbon during leaching in HCl is 1:200 to 1:500.

[0019] Furthermore, when preparing struvite precipitate, NaOH is added to adjust the pH value of the mixed solution to 8-9.

[0020] Furthermore, when preparing struvite precipitate, MgCl2 is added so that the molar ratio of Mg to P is 7:1 to 10:1.

[0021] A sludge-based flocculation-nutrition multifunctional agent is prepared using the above-mentioned preparation method.

[0022] The application of the above-mentioned sludge-based flocculation-nutrition multifunctional agent in sludge recycling.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention can realize deep resource utilization of sludge and fully recover organic matter, nitrogen, phosphorus, etc. contained in the sludge.

[0025] 2. In this process, the process design is fully based on the characteristics of the intermediate products in each link, which can effectively reduce the cost of process reagents.

[0026] 3. The flocculation-nutrient multifunctional agent prepared in this process can simultaneously achieve dehydration and nutrient treatment of slag slurry, effectively improving the resource utilization efficiency of slag slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 This is a flow chart for preparing the flocculation-nutrition multifunctional agent of the present invention. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] A method for preparing a sludge-based flocculation-nutrition multifunctional agent comprises the following steps:

[0031] S1, subjecting the sludge to hydrothermal carbonization reaction under the condition of adding NaOH, obtaining and separating hydrothermal char and nitrogen-rich aqueous phase residue;

[0032] S2, leaching the hydrothermal charcoal in HCl to obtain and separate the acid-leached hydrothermal charcoal and the phosphorus-rich leachate;

[0033] S3, mixing the nitrogen-rich aqueous phase residue and the phosphorus-rich extract, and allowing the mixture to stand to obtain a humic acid precipitate; after the precipitation is sufficient, adding NaOH and MgCl2 to obtain a struvite precipitate;

[0034] S4, placing the acid-soaked hydrothermal charcoal, humic acid precipitate and struvite precipitate in a polydimethyl ammonium chloride solution, stirring and immersing for 30 minutes, and then separating to obtain a solid phase mixture, namely, a sludge-based flocculation-nutrition multifunctional agent.

[0035] In S1, the amount of NaOH added is 2% to 10% of the sludge mass; the hydrothermal carbonization reaction temperature is 180°C to 220°C, the reaction time is 4 hours, and the solid-liquid ratio (W / W) is 1:10; the total nitrogen content of the obtained nitrogen-rich aqueous phase residue is greater than 5000 mg / L.

[0036] In S2, the HCl concentration is 0.1M to 1.0M, the solid-liquid ratio (W / W) of hydrothermal carbon to HCl is 1:200 to 1:500, and the immersion time is not less than 60 minutes; the total phosphorus content of the obtained phosphorus-rich extract is greater than 3000 mg / L.

[0037] In S3, the amount of NaOH added is determined according to the actual pH value of the phosphorus-rich extract, ensuring that the pH value of the mixed solution can be adjusted to 8-9 after adding NaOH.

[0038] In S3, the amount of MgCl2 added is determined according to the actual phosphorus content of the phosphorus-rich extract to ensure that the Mg / P molar ratio after addition is 7:1 to 10:1.

[0039] In S4, the concentration of the polydiallyl dimethyl ammonium chloride solution is 20 wt %, and the solid-to-liquid ratio (W / W) of the acid-soaked hydrothermal charcoal to the polydiallyl dimethyl ammonium chloride solution is 1:20 to 1:50.

[0040] The technical solution of the present invention is specifically described below by the following examples; the raw materials used in the following examples are as follows:

[0041] The wet sludge was dewatered sludge from a municipal sewage treatment plant (water content 80%, total nitrogen 3.2%, total phosphorus 1.8%, organic matter content 45%). The reagents included: NaOH (analytical grade), HCl (0.5 M), MgCl2·6H2O (industrial grade), and polydiallyldimethylammonium chloride (PDDA, 20 wt% solution).

[0042] Example 1

[0043] like Figure 1 As shown, the preparation method of the sludge-based flocculation-nutrition multifunctional agent comprises the following steps:

[0044] Step 1: Take 1kg of wet sludge (80% moisture content), add 5% of the wet sludge mass of NaOH (i.e. 50g), adjust the solid-liquid ratio to 1:10 (add pure water to a total weight of 10kg). Place in a high-pressure reactor, heat to 200℃ at 5℃ / min and maintain for 4 hours. After the reaction, centrifuge to obtain solid hydrothermal carbon (yield 38.2%, specific surface area 215m 2 / g), nitrogen-rich aqueous phase (total nitrogen concentration 5620 mg / L, ammonia nitrogen accounting for 82%).

[0045] Step 2: Take 200g of the hydrothermal carbon obtained in step 1, add 0.5M HCl solution (solid-liquid ratio 1:300, total liquid volume 60L), and mechanically stir for 90 minutes. Centrifuge to obtain acid-leached hydrothermal carbon (total phosphorus residual rate 6.3%, specific surface area increased to 386m 2 / g), phosphorus-rich extract (total phosphorus concentration 3250mg / L, PO4 3- accounting for 91%).

[0046] Step 3: Mix the nitrogen-rich solution (10 L) from step 1 with the phosphorus-rich solution (60 L) from step 2, and let it stand for 2 hours to precipitate humic acid (yield 12.4 g / L). Then, check the pH of the mixed solution to 4.7, slowly add NaOH to pH 8.5, and adjust the pH to Mg. 2+ :PO4 3- MgCl2 (total amount 2.34 kg) was added at a molar ratio of 1.6:1. After stirring for 30 minutes, struvite precipitate was formed (crystal purity > 95%, particle size D50 = 28 μm).

[0047] Step 4: Take 100 g of acid-soaked hydrochar, 124 g of humic acid precipitate, and 860 g of struvite precipitate, and soak them together in 20 wt% PDDA solution (solid-to-liquid ratio 1:30, total liquid volume 6 L). After stirring for 30 minutes, vacuum drying was obtained to obtain a finished multifunctional agent (water content 8.7%).

[0048] Example 2

[0049] like Figure 1 As shown, the preparation method of the sludge-based flocculation-nutrition multifunctional agent comprises the following steps:

[0050] Step 1: Take 1kg of wet sludge (80% moisture content), add 2% of the wet sludge mass of NaOH (i.e. 50g), adjust the solid-liquid ratio to 1:10 (add pure water to a total weight of 10kg). Place in a high-pressure reactor, heat to 180℃ at 5℃ / min and maintain for 4 hours. After the reaction, centrifuge to obtain solid hydrothermal carbon (yield 41.2%, specific surface area 206m 2 / g), nitrogen-rich aqueous phase (total nitrogen concentration 5107 mg / L, ammonia nitrogen accounting for 76%).

[0051] Step 2: Take 200g of the hydrothermal carbon obtained in step 1, add 0.5M HCl solution (solid-liquid ratio 1:300, total liquid volume 60L), and mechanically stir for 90 minutes. Centrifuge to obtain acid-leached hydrothermal carbon (total phosphorus residual rate 6.1%, specific surface area increased to 317m 2 / g), phosphorus-rich extract (total phosphorus concentration 3378 mg / L, PO4 3- accounting for 91%).

[0052] Step 3: Mix the nitrogen-rich solution (10 L) from step 1 with the phosphorus-rich solution (45 L) from step 2, and let it stand for 2 hours to precipitate humic acid (yield 12.4 g / L). Then, check the pH of the mixed solution to 5.4, slowly add NaOH to pH 8.5, and adjust the pH to Mg. 2+ :PO4 3- MgCl2 (total amount 2.40 kg) was added at a molar ratio of 1.6:1. After stirring for 30 minutes, struvite precipitate was formed (crystal purity > 95%, particle size D50 = 27 μm).

[0053] Step 4: Take 200 g of acid-soaked hydrochar, 124 g of humic acid precipitate, and 600 g of struvite precipitate, and immerse them together in 20 wt% PDDA solution (solid-to-liquid ratio 1:30, total liquid volume 6 L). After stirring for 30 minutes, vacuum drying is performed to obtain a finished multifunctional agent (water content 8.5%).

[0054] Example 3

[0055] In this embodiment, the multifunctional agent prepared in Example 1 and Example 2 was applied to the resource treatment of slag slurry, and various indicators of the slag slurry before and after treatment were tested; Figure 1 As shown, the specific process is:

[0056] A subway construction waste slurry (water content 83.5%, liquid limit 52%, plastic limit 23%) was added to the waste slurry at a dry weight ratio of 1.5% (i.e., 15 kg per ton of slurry). The slurry was mechanically stirred for 20 minutes and then allowed to stand for dehydration. The test results are shown in Table 1:

[0057] Table 1 Test results of various indicators before and after slag slurry treatment

[0058]

[0059] It can be seen from the data in Table 1 that the sludge-based flocculation-nutrient multifunctional agent of the present invention can achieve effective flocculation of the slag slurry, thereby obtaining a better dehydration effect, and the multifunctional agent also improves the nutrient content of the slag, so that it can be subsequently used as nutrient soil.

[0060] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0061] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for preparing a sludge-based flocculation-nutrition multifunctional agent, characterized in that: The following steps are involved: The sludge is subjected to hydrothermal carbonization reaction under the condition of adding NaOH to obtain and separate hydrothermal char and nitrogen-rich aqueous phase residue; leach the hydrothermal charcoal in HCl to obtain and separate the acid-leached hydrothermal charcoal and the phosphorus-rich leachate; The nitrogen-rich aqueous phase residue and the phosphorus-rich extract are mixed and allowed to stand to obtain a humic acid precipitate; after the precipitation is sufficient, NaOH and MgCl2 are added thereto to obtain a struvite precipitate; The acid-soaked hydrothermal charcoal, humic acid precipitate and struvite precipitate are placed in a polydiallyl dimethyl ammonium chloride solution, stirred and then separated to obtain the product.

2. The method for preparing a sludge-based flocculation-nutrition multifunctional agent according to claim 1, characterized in that: During the hydrothermal carbonization reaction, the amount of NaOH added is 2% to 10% of the sludge mass.

3. The method for preparing a sludge-based flocculation-nutrition multifunctional agent according to claim 1, characterized in that: The hydrothermal carbonization reaction temperature is 180°C to 220°C.

4. The method for preparing a sludge-based flocculation-nutrition multifunctional agent according to claim 1, characterized in that: The solid-liquid ratio during the hydrothermal carbonization reaction is 1:

10.

5. The method for preparing a sludge-based flocculation-nutrition multifunctional agent according to claim 1, characterized in that: The HCl concentration is 0.1M~1.0M.

6. The method for preparing a sludge-based flocculation-nutrition multifunctional agent according to claim 1, characterized in that: The solid-liquid ratio of the hydrothermal carbon during leaching in HCl is 1:200 to 1:

500.

7. The method for preparing a sludge-based flocculation-nutrition multifunctional agent according to claim 1, characterized in that: When preparing struvite precipitate, NaOH is added to raise the pH value of the mixture to 8-9.

8. The method for preparing a sludge-based flocculation-nutrition multifunctional agent according to claim 1, characterized in that: When preparing struvite precipitate, MgCl2 is added so that the molar ratio of Mg to P is 7:1 to 10:

1.

9. A sludge-based flocculation-nutrition multifunctional agent, characterized in that: It is prepared using the preparation method according to any one of claims 1 to 8.

10. Use of the sludge-based flocculation-nutrition multifunctional agent according to claim 9 in sludge recycling.

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